In many cities wastewater and rainwater are collected together in a combined sewer system. These combined sewer systems create a potential for a combined sewer overflow (CSO). A CSO occurs when a wastewater treatment facility experiences excessive inflow due to wet weather conditions resulting in an overflow or discharge of contaminated water. In some cases, the overflow water backs up into homes or businesses. In order to prevent raw sewage backup into homes and businesses, waste water treatment facilities often divert the overflow into an open stream or river. Accordingly, a CSO event often results in the contamination or rivers, lakes and ocean shores and presents numerous environmental health-related dangers.
The problems associated with CSO events have been addressed by replacing combined sewers with dual collection and disposal systems, providing off-line storage facilities, such as providing underground tunnels, or expanding the capacity of the overloaded waste water treatment facility. However, these solutions require intensive and expensive construction, which can be disruptive to cities and their population. Moreover, separating wastewater and rainwater collection does not completely solve the environmental problems since untreated storm water often carries contaminants washed away from streets.
An alternative option is to use in-line storage using real-time monitoring, which monitors the flow and composition of the fluid in the sewer. When a CSO event is predicted the system reacts by using the pipes as a temporary storage. A real-time control system calculates the unused volume in each of the main arterial pipes and sends command signals to gates, inflatable dams or valves to regulate the flow. Existing in-line storage solutions suffer because the large amount of information required to effectively control the system must be transmitted to a central processor for processing and the communication, monitoring and control require great expense and are prone to failure.